As disclosed in, for example, JP-A-2006-19455 corresponding to US 2006/0001174 and JP-A-2007-81100, a semiconductor device including a semiconductor substrate having a through electrode portion for electrically connecting front and back surfaces of the semiconductor substrate has been known. Such a semiconductor device can be reduced in size.
The electrode portion is formed as follows. Firstly, a through hole extending from the front surface to the back surface of the semiconductor substrate is formed by, for example, an etching technique. Then, a first conductor, an insulation layer, and a second conductor are formed in the through hole by, for example, a sputtering technique and a chemical vapor deposition (CVD) technique. The first conductor has a tube shape and is formed on an inner surface of the through hole. The insulation layer has a tube shape and is formed on an inner surface of the first conductor. The second conductor has a column shape and is formed in a hollow of the insulation layer so that the hollow can be filled with the second conductor.
For example, the first conductor is used as a signal line, and the second conductor is used as a ground line. The second conductor is shielded by the first conductor so that noise in the first conductor as a signal line can be reduced.
To increase such a shield effect, it is preferable to increase a capacitance of a capacitor constructed with the first and second conductors spaced by the insulation layer.
The capacitance can be increased by increasing the area of the first and second conductors. However, in the conventional semiconductor device, an increase in the area of the first and second conductors results in an increase in a diameter of the through hole. As a result, the through electrode is increased in size, and the semiconductor device is increased in size.